OF THE SKULL IN THE AMPHIBIA ITEODELA. 193 



vertically ; the upper lobe is the ascending process (fig. 1, a.p) ; it has coalesced with 

 the alisphenoidal crest near the top. 



Tbe lower lobe, or pedicle (fig. 2, pd), is much less distinct than the upper, and seems 

 like a swelling on the under face of that cartilage ; the orbitomasal and Vidian nerves 

 pass between this swelling and the skull-wall under the ascending process. The outer 

 or otic process (ot.p) applies itself, like a snail's foot, to the antero-external face of the 

 ear-capsule ; it is rounded below (fig. 2), but raised into a distinct ridge above (fig. 1), 

 which reaches to the anterior ampulla (a.sc). In this stage the otic process is quite 

 like what is seen in newly metamorphosed Batrachia, notably in Pseudis paradoxa. 



The suspensorium is confluent with the skull only by its ascending process ; the other 

 process, right and left, plays freely on the auditory capsule, and is set in a bed of 

 delicate connective tissue. The fore margin of tbe suspensorium shows no pterygoid 

 process, although the ethmo-palatine cartilage (e.jia) is quite apparent. 



The lozenge-shaped dentigerous palatine bone has already sent backwards a large, flat, 

 edentulous pterygoid process, so that we have the widely distributed ptery go-palatine 

 bone (p.pg) *. 



The whole bone reaches from the quadrate to the vomer (fig. 2), and the two bones 

 with the two vomers (v) mark out half a long ellipse. The vomers are falcate, and nearly 

 meet in the middle by their broad hooked end ; they are dentigerous, and are about half 

 as wide as the pterygo-palatmes. In front of the vomers we have the median nasal 

 passage (m.n.p) in the middle, and the trabecular cornua (c.tr) at the sides. 



In front of these there is the dentary margin of the premaxillary (which is not double 

 as in Proteus and Ilenobranchus) ; above (fig. 1) its nasal processes (n.px) are large and 



* As the parasphenoid is the great primordial basal bony plate, so is this the first of the palatals, as we see in 

 the Dipnoi, which have so few bony lamina} applied to the solid chondrocranium, a step beyond the Ohinneroids and 

 ordinary Selachians. Higher up it is curious to see the persistency of the pterygo-palatine. In the generalized 

 Hatteria (see Giinther, Phil. Trans, part ii. 1807, plate i. fig. 2) the huge pterygoid has a large flat anterior 

 part, which reaches and articulates with the corresponding vomer. In Anguis fragilis this fore part of the 

 pterygoid boue is separate as a " mesopterygoid." The true longitudinal palatine of the Hatteria lies outside the 

 vomer and pterygoid. 



In Birds tho pterygoid grows forward to the vomer (generally composed of a right and left bony centre) ; but, as 

 in Anguis fragilis, there is afterwards a separate piece cut off as a mesopterygoid. In all the Carinata), except the 

 Woodpeckers and the Galline and Anserine groups, this takes place ; and, oddly, the new bone soon coalesces 

 with the inner edge of the great palatine, which is longitudinally placed, lies outside the pterygo-vomerine 

 6eries, and reaches from the pterygoid to the front of the nasal labyrinth. I have shown that Picumnus minutus 

 has a postpalatine, like Cipwjis and Notophihalmus ; and the Passerinoe have an additional cartilage besides 

 the ethmo-vomerine and pterygoid (the pterygoid of a bird is formed in nascent cartilage and is cartilaginous behind) ; 

 and this transpalatiue occurs in Siredon. In the Bird it ossifies separately, and then coalesces with the outer part of 

 the great palatine, as the mesopterygoid does with the inner edge. 



Further, the ethmo-palatine of the Frog, when the transverse bony plate has grafted itself on the cartilage, 

 corresponds with the os uncinatum of the Bird (C'on/tJiai.v, Trogon, Psittaeus) ; and this anterior transverse bone is fore- 

 shadowed in those Urodeles that have a transverse bony palatine running under their ethmo-palatine cartilage, as in 

 Amblystoma, Spelerpes, and Desmognathus. Stepping, then, across the wide space between the Dipnoi, the low Urodeles. 

 and the larva? of the higher kinds to the Bird, we have one safe determination to stand upon, namely, the relation of 

 the primordial pterygo-palatine to the corresponding vomer. The other parts that come in, in tho metamorphosis of 

 the Urodeles, or in the ascent up the tribes, are new things — sjiecializations. 



